Use a single ToplevelWindowEventHandler for the ash::Shell

ash/wm/panels/panel_window_event_handler.cc

Index: ash/wm/panels/panel_window_event_handler.cc
diff --git a/ash/wm/panels/panel_window_event_handler.cc b/ash/wm/panels/panel_window_event_handler.cc
index cb4946991951c5df45c5c3d6c72c2c38a3791f50..f056935accf756a0b15e0563da033ebdcad880c5 100644
--- a/ash/wm/panels/panel_window_event_handler.cc
+++ b/ash/wm/panels/panel_window_event_handler.cc
@@ -4,6 +4,8 @@
 
 #include "ash/wm/panels/panel_window_event_handler.h"
 
+#include "ash/metrics/user_metrics_recorder.h"
+#include "ash/shell.h"
 #include "ash/wm/window_state.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
@@ -13,8 +15,7 @@
 namespace ash {
 namespace internal {
 
-PanelWindowEventHandler::PanelWindowEventHandler(aura::Window* owner)
-    : ToplevelWindowEventHandler(owner) {
+PanelWindowEventHandler::PanelWindowEventHandler() {
 }
 
 PanelWindowEventHandler::~PanelWindowEventHandler() {
@@ -27,10 +28,12 @@ void PanelWindowEventHandler::OnMouseEvent(ui::MouseEvent* event) {
       event->IsOnlyLeftMouseButton() &&
       target->delegate()->GetNonClientComponent(event->location()) ==
           HTCAPTION) {
+    ash::Shell::GetInstance()->metrics()->RecordUserMetricsAction(
+        ash::UMA_PANEL_MINIMIZE_CAPTION_CLICK);
     wm::GetWindowState(target)->Minimize();
+    event->StopPropagation();
     return;
   }
-  ToplevelWindowEventHandler::OnMouseEvent(event);
 }
 
 void PanelWindowEventHandler::OnGestureEvent(ui::GestureEvent* event) {
@@ -39,11 +42,12 @@ void PanelWindowEventHandler::OnGestureEvent(ui::GestureEvent* event) {
       event->details().tap_count() == 2 &&
       target->delegate()->GetNonClientComponent(event->location()) ==
           HTCAPTION) {
+    ash::Shell::GetInstance()->metrics()->RecordUserMetricsAction(
+        ash::UMA_PANEL_MINIMIZE_CAPTION_GESTURE);
     wm::GetWindowState(target)->Minimize();
     event->StopPropagation();
     return;
   }
-  ToplevelWindowEventHandler::OnGestureEvent(event);
 }
 
 }  // namespace internal